1. Field of the Invention
The present invention generally relates to signal communications, and more particularly, to an architecture and protocol for processing signal communications between a frequency translation apparatus, which may be referred to herein as a frequency translation module (FTM), and an integrated receiver-decoder (IRD).
2. Background Information
In a satellite broadcast system, one or more satellites receive signals including audio and/or video signals from one or more earth-based transmitters. The satellite(s) amplify and rebroadcast these signals to signal receiving equipment at the dwellings of consumers via transponders that operate at specified frequencies and have prescribed bandwidths. Such a system includes an uplink transmitting portion (i.e., earth to satellite(s)), an earth-orbiting satellite receiving and transmitting portion, and a downlink portion (i.e., satellite(s) to earth).
In dwellings that receive signals from a satellite broadcast system, signal receiving equipment may be used to frequency shift the entire broadcast spectrum of the satellite(s), and frequency stack the resultant output onto a single coaxial cable. That is, the frequency spectrum associated with one set of signals is shifted to the frequencies adjacent to, or different from, the frequency spectrum of another set of signals, thereby positioning or stacking the sets of signals in the frequency domain. As the number of satellites within a satellite broadcast system increases, and with the proliferation of high definition satellite channels, a point will be reached where the total bandwidth required to accommodate all of the satellites will exceed the transmission capability of the coaxial cable. It has become necessary for the satellite decoder industry to implement more satellite slots into their distribution systems. To provide for the increased number of satellite slot transmissions a more elaborate means for satellite configurations selection has been developed called the frequency translation module (FTM) method.
An FTM for delivering satellite signals to Integrated Receiver Decoders (IRDs) comprises one or more input/outputs (I/Os) coupled to low noise block amplifiers (LNB), and one or more input/outputs coupled to IRDs. The FTM module operative to receive requests from the IRD indicating desired satellite program channels. In response to the request from the IRD, the FTM module controls the appropriate LNB such that the requested channel, or block of channels is delivered to the FTM IO. The FTM module then may frequency shift the requested channel to a second frequency corresponding to an unoccupied frequency on the transmission line to the IRDs. The FTM module zo then communicates to the requesting IRD the frequency on which the requested channel is being supplied. When the FTM is operative to couple a plurality of satellite program channels to a plurality of IRDs, the FTM individually commands each LNB to supply the desired channels or band of channels, and outputs each of the desired channels or band of channels on the same transmission line to the IRDs, with each desired channel or band of channels modulated at unique frequencies.
The FTM uses a UART controlled 2.3 MHz, Frequency Shift Key (FSK) modulation scheme to communicate selection commands to the IRDs and the FTM. Present day satellite decoder systems use complicated PLL and superhetrodyne receivers to amplify the narrow band required for FSK reception with no conversion or detection. This results in an undesirably expensive implementation that must be implemented in each IRD and FTM, the cost being far more than the cost of the legacy DiSEqC communication system. There is a need for a low cost FSK signal processing means with frequency filter, amplitude limiting, and wide dynamic range without the need for an expensive AGC system. The present invention described herein addresses this and/or other problems.